[FPSPACE] Oberg's USA-193 stories today for NBC

[James Oberg]

Oberg's USA-193 stories today for NBC

two links...

Heading off a toxic iceberg from space

Concern about hydrazine fuel leads to Pentagon's satellite intercept plan

http://www.msnbc.msn.com/id/23166344/

By James Oberg, NBC News space analyst // Special to MSNBC

updated 5:56 p.m. CT, Thurs., Feb. 14, 2008



and



Q&A: Destroying a broken spy satellite

What will happen when missiles are fired from Navy cruiser

By James Oberg, NBC News space analyst // Special to MSNBC

updated 1:41 p.m. CT, Thurs., Feb. 14, 2008




full text:

Heading off a toxic iceberg from space

Concern about hydrazine fuel leads to Pentagon's satellite intercept plan

http://www.msnbc.msn.com/id/23166344/

By James Oberg, NBC News space analyst // Special to MSNBC

updated 5:56 p.m. CT, Thurs., Feb. 14, 2008

   HOUSTON - Less than a month ago, White House officials said a falling spy satellite would likely pose little threat to humans - but on Thursday, the Pentagon said President Bush himself approved an unorthodox plan to destroy the satellite with a missile strike.

   What could warrant such a change of heart? It's the realization that the spacecraft could be bringing a toxic iceberg back down to Earth.

   Aboard the 2.5-ton derelict satellite, designated "USA-193," is a fuel tank containing half a ton of hydrazine. Since the satellite went dead within hours after launch 14 months ago, the fuel has not been depleted by normal rocket maneuvers.

   Hydrazine is a nasty chemical that could poison the area where it is released. Until recently, U.S. officials were saying that the tank would be crushed as the satellite fell through the atmosphere, sometime in early March. If that were the case, the toxic hydrazine would almost certainly be burned off and safely dispersed during the fiery fall.

   NASA Administrator Michael Griffin sketched out a different scenario, however, during Thursday's news conference with Gen. James Cartwright, the vice chairman of the Joint Chiefs of Staff. Griffin said NASA experts calculated that the hydrazine was frozen solid due to the satellite's yearlong drift through the cold of space. The tank, with its half-ton ice core of hydrazine, would thus become one of the most perfect re-entry vehicles ever to fall back to Earth.

   Griffin explained that the contents of the tank could turn to slush during the fall, but would very likely survive and leak toxic gas over the crash site. Another expert told msnbc.com privately that the solid ice would provide structural support against the 20 to 25 G's of deceleration experienced by the satellite during re-entry.

 

Safety first?

   Pentagon officials said it was that safety concern, rather than the intention to test a potential anti-satellite weapon, which led them to develop the plan for a missile intercept. They hope the impact of the warhead on a modified Standard Missile-3, or SM-3, will shatter the satellite - and particularly the spherical hydrazine tank. The first shot could occur as early as next week, after the space shuttle Atlantis' return from its mission to the international space station.

   Would a direct hit be required? Experts on space debris told msnbc.com that even a glancing blow would likely be enough. The force of a missile hitting an orbiting object is much more violent than the force of a bullet striking a target, or even an anti-aircraft missile hitting an airplane. In the space case, the tremendous speed of the impact carries so much kinetic energy that both 

vehicles literally explode due to the hypersonic shock waves sweeping through their structures.

   If the missile strike leads to such a disintegration, sharp observers should be able to spot the ice fragments from the fuel tank. As the fragments evaporate in direct sunlight, they could create mini-comets visible from Earth's surface, lasting for hours before dispersing.

   Pentagon officials said the intercept would occur within range of military optical and radar sensors. Their goal would be to confirm the existence of dispersed hydrazine in the debris. If the sensors don't show the fuel dispersing, missile operators would target the fragment judged most likely to be the still-surviving fuel tank. A second shot could occur within a day or two of the first. 

 

Giving the missiles a boost

   Last week's orbital readings indicated that the satellite was circling Earth at an altitude between 160 and 168 miles (255 and 268 kilometers) and descending at an increasing rate, currently about six-tenths of a mile (1 kilometer) per day. Gen. Cartwright said the intercept would be attempted when the satellite descended to about 150 miles (240 kilometers).

   The SM-3 has typically been used for testing the Pentagon's missile defense system, and reaches a nominal maximum altitude of just 100 miles (160 kilometers). For the satellite intercept, three missiles - one each on three different AEGIS-class Navy cruisers - will be modified to reach the higher altitude. 

   This isn't the first time hydrazine has posed a problem in space: The fuel freezes at temperatures below 36 degrees Fahrenheit (2 degrees Celsius), and satellites without active heating will drop to temperatures below that - as a case involving the Soviet Salyut 7 space station demonstrated dramatically in 1985.

   After Salyut 7's power system failed, the water in its supply tanks froze solid, along with the hydrazine in its propulsion system. A pair of cosmonauts reached the icy station and were able to activate its electrical system, and then carefully thawed the frozen tanks. 



Q&A: Destroying a broken spy satellite

What will happen when missiles are fired from Navy cruiser

By James Oberg, NBC News space analyst // Special to MSNBC

updated 1:41 p.m. CT, Thurs., Feb. 14, 2008

 

What will they use to shoot at and destroy the satellite?

An AEGIS-class cruiser will fire modified SM-3 missiles from a position northwest of Hawaii, as the satellite approaches on a directly overhead path.

 

What was this satellite doing, and why is it falling?

The satellite was launched 14 months ago to test a new generation of optical and radar reconnaissance sensors, but its control computer failed almost immediately.

 

What will it look like? Will there be a big spectacle?

After the initial launch, the missile warheads will maneuver by firing steering rocket pulses appearing as sideways flashes from its main body, which will be watched on telescope trackers onboard the launch ship. A flare of light will mark a successful intercept and the bright target blip may turn to a cloud of smaller blips.

 

Will we be able to see anything from Earth?

As the satellite disintegrates from the impact, the unused rocket fuel should make an expanding cloud in the sky that might be visible from Hawaii, depending on whether or not it is day or night. The cloud may persist for 20-30 minutes as it orbits Earth at 5 miles per second.

 

What potential dangers or risks are involved?

Planners must make certain that other objects are not in the line of fire, although the rocket's limited altitude capability should keep it well short of valuable spacecraft such as the international space station.

 

What happens to the debris?

The debris will burn up in days or weeks, because of the target's very low altitude and because small fragments are much more severely slowed down by air drag than large intact objects.

 

Why can't they just let the satellite fall from orbit naturally?

Pieces from satellites of this size tend to reach the ground, but predicting where is impossible. Heavy objects have a very slight chance of hitting somebody, and unused rocket fuel might conceivably contaminate small areas. Worst of all, top secret hardware such as sensor equipment or the control computer's memory unit might be recovered and be exploited by hostile intelligence services.

 

Can the United States do this unilaterally?

Yes, there are no legal sanctions on any nation doing anything it wants to its own property in space. In fact, since each nation is responsible for damage caused by any of its space objects, it can be argued that the United States is obligated by international law to do something like this.

 

Will this action anger any other countries?

The usual suspects, both overseas and domestically. The Russians might feel compelled to dust off their own ground-launched and air-launched anti-satellite weapons or use a standard anti-missile missile from their test rangein Kazakhstan. China can't complain, but North Korea and Iran will. In the United States, groups lobbying against U.S. 'space weaponziation' will see it as proof the United States wants to build - or secretly, already has built - such weapons all along. But all this noise may focus attention on the wider issue of weapons in space (not Earth-launched weapons against space targets).

 

How is this different from China's satellite shootdown last year?

In technical terms, it's not very different, although the Chinese rocket reached a lot farther into space than the U.S. system is capable of. In ethical terms, the U.S. action is supposedly a remedial measure taken to enhance safety, while the Chinese action looked a lot more like a weapons test to threaten other countries. The U.S. rocket to be used does not appear to be even capable of reaching operational satellites of other nations.